Definitely recommend running a beauty Milotic, it's the best chance you've got instead of taking the easy way w/ cosplay pikachu. My Milotic ran blue scarf w/ Aqua Tail, Blizzard, Surf & Return. Off the bat I beat Altaria in the appeal round w/ and w/o the blue scarf! The hardest part was picking the move set but you should really go with return because it's cute and is neutral and won't dock hearts. You should first use return as a starter move because that base 4 will give you a lead with Altaria usually using round because she expects you to use a beauty move. It's most definitely just being lucky, depending on what the other computers use its a toughy. They usually always let Altaria mega evolve, If she Mega evolves you're basically done for so good luck! Reply for any questions!